1. Field of the Invention
The present invention relates to a conductive rubber member suitable for a conductive roller (e.g., a charge-imparting roller, an image-transfer roller, a development roller, a toner-supply roller, or a cleaning roller), a cleaning blade, a transfer belt, etc., for use in an image-forming apparatus such as an electrophotographic or toner-jet-type copying machine or printer.
2. Background Art
Conductive rollers employed in image-forming apparatuses such as copying machines and printers are required to have a non-staining property to a photoreceptor and other elements, appropriate conductivity, etc.
In this regard, the present inventors previously proposed a conductive roller having an elastic layer formed of an epichlorohydrin base rubber, a surface of the layer having been treated with a treatment solution containing an isocyanate compound (see Japanese Patent No. 3444391 and Japanese Patent Application Laid-open (kokai) Nos. 2004-191960 and 2004-191961).
Addition of an ion-conductivity-imparting agent to a rubber member is one possible approach to attain lower electrical resistance. However, when an ion-conductivity-imparting agent is added in a large amount, even though a surface-treated layer has been provided, the electrical resistance of the rubber member varies considerably due to environmental factors, and bleeding of the ion-conductivity-imparting agent occurs to thereby stain a photoreceptor, in some cases.
In order to prevent bleeding of an ion-conductivity-imparting agent or to enhance permanent compressive strain and abrasive machining performance, one possible approach is to add sulfur or a sulfur-containing vulcanization accelerator. However, when such an additive is employed in a large amount, electrical resistance increases in some cases.